Phase 3.1 WIP: Riverpod migration (client_app Auth + ChatOpening)

- Add phase3.1 requirement and implementation plan docs
- Add Riverpod dependencies to both client_app and mitra_app
- Wrap both app roots with ProviderScope
- Migrate client_app AuthBloc → AuthNotifier (@riverpod annotation)
- Migrate client_app ChatOpeningBloc → chatPricingProvider (FutureProvider)
- Update router to use Riverpod-based auth state for redirects
- Update all auth screens (display name, register, OTP, force register)
- Update home screen and pricing bottom sheet
- Add android:usesCleartextTraffic for dev HTTP access on both apps
- mitra_app prepared with ProviderScope + ApiClient provider (blocs next)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client_app/lib/core/chat/chat_opening_provider.dart

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+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import '../api/api_client_provider.dart';
+
+part 'chat_opening_provider.g.dart';
+
+class PriceTier {
+  final int durationMinutes;
+  final int price;
+  final String label;
+
+  PriceTier({required this.durationMinutes, required this.price, required this.label});
+
+  factory PriceTier.fromJson(Map<String, dynamic> json) {
+    return PriceTier(
+      durationMinutes: json['duration_minutes'] as int,
+      price: json['price'] as int,
+      label: json['label'] as String,
+    );
+  }
+}
+
+class PricingData {
+  final List<PriceTier> tiers;
+  final bool freeTrialEligible;
+  final int freeTrialDurationMinutes;
+
+  const PricingData({
+    required this.tiers,
+    required this.freeTrialEligible,
+    this.freeTrialDurationMinutes = 5,
+  });
+}
+
+@riverpod
+Future<PricingData> chatPricing(Ref ref) async {
+  final apiClient = ref.read(apiClientProvider);
+  final response = await apiClient.get('/api/client/chat/pricing');
+  final data = response['data'] as Map<String, dynamic>;
+  final tiersJson = data['tiers'] as List<dynamic>;
+  final tiers = tiersJson.map((t) => PriceTier.fromJson(t as Map<String, dynamic>)).toList();
+  final freeTrial = data['free_trial'] as Map<String, dynamic>;
+
+  return PricingData(
+    tiers: tiers,
+    freeTrialEligible: freeTrial['eligible'] as bool? ?? false,
+    freeTrialDurationMinutes: freeTrial['duration_minutes'] as int? ?? 5,
+  );
+}

client_app/lib/core/chat/chat_opening_provider.g.dart

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+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'chat_opening_provider.dart';
+
+// **************************************************************************
+// RiverpodGenerator
+// **************************************************************************
+
+String _$chatPricingHash() => r'53ca829d46f7ba3b481e7a6b54482c62f9fe3ad0';
+
+/// See also [chatPricing].
+@ProviderFor(chatPricing)
+final chatPricingProvider = AutoDisposeFutureProvider<PricingData>.internal(
+  chatPricing,
+  name: r'chatPricingProvider',
+  debugGetCreateSourceHash:
+      const bool.fromEnvironment('dart.vm.product') ? null : _$chatPricingHash,
+  dependencies: null,
+  allTransitiveDependencies: null,
+);
+
+@Deprecated('Will be removed in 3.0. Use Ref instead')
+// ignore: unused_element
+typedef ChatPricingRef = AutoDisposeFutureProviderRef<PricingData>;
+// ignore_for_file: type=lint
+// ignore_for_file: subtype_of_sealed_class, invalid_use_of_internal_member, invalid_use_of_visible_for_testing_member, deprecated_member_use_from_same_package